Load shoulders are often used in wellbores to support various tools and equipment. A load shoulders is typically a conical or flat surface that encircles a bore within a tubular member. A load shoulder, also called a “no-go” shoulder, prevents tools having diameters larger than the inner diameter of the load shoulder from passing through. The load shoulder has the capacity to support the weight of the tool or device that lands on it.
A load shoulder is employed wherein wells are drilled by a method called casing-while-drilling. In this method, rather than a string of drill pipe being employed to drill the well, the operator drills the well with a string of casing or liner, and the casing or liner is subsequently cemented in the well. The term “casing” refers to well pipe that is cemented in the well and extends all the way to the wellhead. The term “liner” refers to pipe that is cemented in the well but extends only a short distance above the lower end of a previously installed string of casing. For convenience, both casing and liner will be referred to herein as casing. In the casing-while-drilling technique, a sub or tubular member is connected into the casing string near or at the lower end of the casing string. The tubular member has a no-go shoulder located within its bore.
The operator lowers a bottom hole assembly (“BHA”) into the casing string. The BHA has a profile that will land on the no-go shoulder. A lower portion of the BHA extends through the no-go shoulder and out the lower end of the casing. A drill bit and optionally other equipment are located on this lower portion. Typically the BHA has a connector member that includes dogs that extend out and engage an annular recess in the tubular member to prevent the BHA from moving upward from the no-go shoulder when the casing string weight is imposed on the drill bit during drilling. Also, torque needs to be transmitted from the casing string to the BHA. Typically, spring-biased dogs are employed to spring out and engage circumferentially spaced-apart recesses or splines located in the bore of the tubular member. The operator employs a casing gripper at the surface to grip the casing and rotate it. The casing gripper attaches to a top drive of the drilling rig.
While this type of casing drilling is successful, the spring-biased dogs that serve to transmit torque from the casing to the BHA add some complexity to the BHA. Also, in small diameter wellbores, there may be inadequate room to mount spring biased dogs for transmitting torque.